1. Field of the Invention
The present invention relates to the manufacture of glass articles, particularly panels comprised of a metal frame holding individual pieces of panes of curved or beveled glass, such as works of art, and the prevention of glass breakage and solder or resin flow during electrodeposition and heat treatment of protective coatings on the metal frame or came and glass pieces assembled therein.
2. Description of the Background Art
Works of art are often made of a number of flat, curved or beveled glass pieces or panes which are mounted in a brass came in which the joints of the came are soldered or welded with lead. The brass came typically discolors over time and, in order to overcome the discoloration problem, a nickel coating is applied on the surface of the brass came to obtain a glossy surface. Thereafter, a transparent resin coating is applied, and the coated surface may be painted to prevent discoloring. In this regard, various techniques for processing the surfaces are disclosed in Korean Patent application No. 10-1999-0000897. However, the glass pieces or panes are easily broken during known electrodeposition coating and heat hardening processes.
Accordingly, it is an object of the present invention to provide a process of surface coating glass panels which overcomes the problems encountered in the conventional art.
In order to achieve the above object, there is provided a surface treatment process which includes the steps of pre-processing the assembled article of came and glass pieces, electrodepositing a coating and paint, and stepwise hardening the coated and painted article.
The surface treatment method broadly involves the following steps.
(A) Pre-processing of the assembled came and glass pieces;
(B) Electrodeposition coating of the assembled pieces and came; and
(C) Step by step heat hardening of the coated came and glass.
The individual steps will each be explained in detail.
(A) Pre-Processing
The preprocessing involves removing non-conductive foreign substances which may adhere to the glass surfaces and is implemented by an ultrasonic wave treatment, electrolytic and fat removal.
The assembled article comprised of came and glass pieces is immersed in a solvent having a temperature of 50xcx9c80xc2x0 F. and is subjected to application of ultrasonic waves for 1xcx9c5 minutes. Foreign substances such as fat attached in the grooves or on the surfaces of the article are removed by the ultrasonic wave treatment. The solvent may comprise a water-soluble solvent containing 3xcx9c5 W % sodium soda, 2xcx9c3 W % phosphoric acid, 1xcx9c2 W % caustic soda, and 0.1xcx9c3.0 W % of an interfacial activator in an organic solvent such as trichloroethylene, benzene, toluene, xylene or the like.
The above ultrasonic wave processed article is then immersed in a water soluble solvent containing 0.2xcx9c0.5 W % caustic soda, 2xcx9c3 W % phosphoric acid, 1xcx9c1.5 W % sodium carbonate, and 0.2xcx9c0.05 W % of an interfacial activator. A cathode of nickel, stainless steel, aluminum or brass may be used, and a zinc and zinc die casting may be used for the anode, and the article is electrolyticly processed at a current density of 5xcx9c10 Am/dm2 for 30xcx9c60 seconds. This results in oxidation of the fat components by oxygen gas at the anode, and removal of floating components by hydrogen gas at the cathode.
Even after alkali fat removal and electrolytic fat removal pre-processing steps have been performed, an oxide film or undissolved coating may still remain on the non-conductive surfaces which is detrimental to the subsequent coating steps which take place. Therefore, 5xcx9c20 W % sulfuric acid or hydrochloric acid are added to remove the remaining film or coating. At this time, the immersion time is 30xcx9c60 seconds.
B) Electrodeposition Steps
A copper coating is first provided as a substrate coating for a nickel coating to enhance a smoothness and removing cracks. The copper is electrodeposited in an aqueous bath containing 15xcx9c30 W % copper and 4xcx9c10 W % sulpheric acid for 5xcx9c20 minutes based on a cathode current density of 1xcx9c10 Am/dm2, an anode current density of 0.5xcx9c5 Am/dm2.
A nickel coating is then applied to achieve a glossy surface of uniform thickness on the article. The nickel surface is electrodeposited at a cathode current density of 1xcx9c10 Am/dm2 in a water solution containing 24xcx9c45 W % sulphuric acid, 3.8xcx9c6 W % nickel chloride, and 3xcx9c5 W % boron. At this time, the anode is the nickel plate, and the nickel coating operation is performed by a blowing method in which air is blown from the lower portion of the working place for thereby flowing the liquid.
The preprocessed came and glass pieces are ultrasonically rinsed for 1xcx9c5 minutes. The rinsed article is then connected with the anode in the electrodeposition container, and a current having a certain density is applied thereto to electrodeposit a protective coating such as a variable 14-15 W % acryloyl resin type albrifin resin (England, Atotech, Co.), and 0.002 W % paint. Any electrodeposition apparatus may be used to provide a current density of 40xcx9c50 Am/dm2 for 30xcx9c180 seconds.
(C) Step-by-Step Heat Hardening
The hardening process of the present invention is directed to preventing flow of resin and lead solder and the glass from being broken when it is dried at a high temperature. The hardening process of the present invention includes the following steps.
a. The electrodespotion processed article is dried for 35xcx9c50 minutes at 45xcx9c55xc2x0 in a pre-drying step.
b. The pre-dried article is heated to a temperature of 130xcx9c145xc2x0 for 40xcx9c60 minutes to prevent the flow of resin and lead.
c. The temperature increased article is dried for 90xcx9c150 minutes.
d. The dried article is gradually cooled for to prevent the glass from being broken due to the quick cooling.
The drying temperature of step (b) is significantly lower than the conventional drying temperature of about 170xc2x0.
The following Examples of the present invention will explain the invention in more detail.